## What is music21?

Music21 is a set of tools for helping scholars and other active listeners answer questions about music quickly and simply. If you’ve ever asked yourself a question like, “I wonder how often Bach does that” or “I wish I knew which band was the first to use these chords in this order,” or “I’ll bet we’d know more about Renaissance counterpoint (or Indian ragas or post-tonal pitch structures or the form of minuets) if I could write a program to automatically write more of them,” then music21 can help you with your work.

## How simple is music21 to use?

Extremely. After starting Python and typing "from music21 import *" you can do all of these things with only a single line of music21 code:

Display a short melody in musical notation:
converter.parse("tinynotation: 3/4 c4 d8 f g16 a g f#").show()

Print the twelve-tone matrix for a tone row (in this case the opening of Schoenberg's Fourth String Quartet):
print (serial.rowToMatrix([2,1,9,10,5,3,4,0,8,7,6,11]) )

or since all the 2nd-Viennese school rows are already available as objects, you can type:
print (serial.getHistoricalRowByyName('RowSchoenbergOp37').matrix() )

Convert a file from Humdrum's **kern data format to MusicXML for editing in Finale or Sibelius:
converter.parse('/users/cuthbert/docs/composition.krn').write('musicxml')

With five lines of music21 code or less, you can:

Prepare a thematic (incipit) catalog of every Bach chorale that is in 3/4:

catalog = stream.Opus()
for workName in corpus.getBachChorales():
work = converter.parse(workName)
firstTS = work.flat.getTimeSignatures()[0]
if firstTS.ratioString == '6/8':
catalog.append(work.measureRange(0,2))
catalog.show()

Google every motet in your database that includes the word ‘exultavit’ in the superius (soprano) part (even if broken up as multiple syllables in the source file) to see how common the motet's text is:

import webbrowser
for motet in listOfMotets:
superius = motet[0]
lyrics = text.assembleLyrics(part)
if 'exultavit' in lyrics:

Add the German name (i.e., B♭ = B, B = H, A♯ = Ais) under each note of a Bach chorale and show the new score:

bwv295 = corpus.parse('bach/bwv295')
for thisNote in bwv295.flat.notes:
bwv295.show()

Of course, you are never limited to just using five lines to do tasks with music21. In the demos folder of the music21 package and in the sample problems page (and throughout the documentation) you’ll find examples of more complicated problems that music21 is well-suited to solving, such as cataloging the rhythms of a piece from most to least-frequently used.

Music21 builds on preexisting frameworks and technologies such as Humdrum, MusicXML, MuseData, MIDI, and Lilypond but music21 uses an object-oriented skeleton that makes it easier to handle complex data. But at the same time music21 tries to keep its code clear and make reusing existing code simple. With music21 once you (or anyone else) has written a program to solve a problem, that program can easily become a module to be adapted or built upon to solve dozens of similar (but not identical) problems.

## Latest music21 News

[June 16, 2015 14:30 pm] « » [music21]

First we start the cluster system with ipcluster start, which on this six-core Mac Pro gives me 12 threads. Then I'll start iPython notebook with ipython notebook.

In [1]:
from __future__ import print_functionfrom IPython import parallelclients = parallel.Client()clients.block = Trueprint(clients.ids)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

Now I'll create a view that can balance the load automatically.

In [2]:
view = clients.load_balanced_view()

Next let me get a list of all the Bach chorales' filenames inside music21:

In [3]:
from music21 import *chorales = list(corpus.chorales.Iterator(returnType = 'filename'))chorales[0:5]
['bach/bwv269', 'bach/bwv347', 'bach/bwv153.1', 'bach/bwv86.6', 'bach/bwv267']

Now, I can use the view.map function to automatically run a function, in this case corpus.parse on each element of the chorales list.

In [4]:
view.map(corpus.parse, chorales[0:4])
Out[4]:
[<music21.stream.Score 4467044944>, <music21.stream.Score 4467216976>, <music21.stream.Score 4465996368>, <music21.stream.Score 4465734224>]

Note though that the overhead of returning a complete music21 Score from each processor is high enough that we don't get much of a savings, if any, from parsing on each core and returning the Score object:

In [5]:
import timet = time.time()x = view.map(corpus.parse, chorales[0:30])print("Multiprocessed", time.time() - t)t = time.time()x = [corpus.parse(y) for y in chorales[0:30]]print("Single processed", time.time() - t)
Multiprocessed 1.7093911171Single processed 2.04412794113

But let's instead just return the length of each chorale, so we don't need to pass much information back to the main server. First we need to import music21 on each client:

In [6]:
clients[:].execute('from music21 import *')
Out[6]:
<AsyncResult: finished>

Now, we'll define a function that parses the chorale and returns how many pitches are in the Chorale:

In [7]:
def parseLength(fn):    c = corpus.parse(fn)    return len(c.flat.pitches)

Now we're going to see a big difference:

In [8]:
t = time.time()x = view.map(parseLength, chorales[0:30])print("Multiprocessed", time.time() - t)t = time.time()x = [parseLength(y) for y in chorales[0:30]]print("Multiprocessed", time.time() - t)
Multiprocessed 0.59440112114Multiprocessed 2.97019314766

In fact, we can do the entire chorale dataset in about the same amount of time as it takes to do just the first 30 on single core:

In [9]:
t = time.time()x = view.map(parseLength, chorales)print(len(chorales), 'chorales in', time.time() - t, 'seconds')
347 chorales in 5.31799721718 seconds

I hope that this example gives some sense of what might be done w/ a cluster situation in music21. If you can't afford your own Mac Pro or you need even more power, it's possible to rent an hour of cluster computing time at Amazon Web Services for just a few bucks.

[June 16, 2015 13:38 pm] « » [music21]

The newest version of the beta 2.0 track of music21 has been released. A reminder that the 2.0 track involves potentially incompatible changes w/ 1.X so upgrade slowly and carefully if you need existing programs to work. Changes are being made to simplify and speed up usage and make the system more expandable for the future.

Major Changes

• Complete rewrite of TinyNotation. Tinynotation was one of the oldest modules in music21 and it showed — I was still learning Python when I wrote it. It documents a simple way of getting notation into music21 via a lily-like text interface. It was designed to be subclassable to make it work on whatever notation you wanted to use. And technically it was, but it was so difficult to do as to be nearly impossible. Now you’ll find it much simpler to subclass. Demos of subclassing are included in the code (esp. HarmonyNotation, and trecento.notation); a tutorial to come soon.
• backwards incompatible changes: (1) you used to be able to specify an initial time signature to Tinynotation as corpus.parse(“tinynotation: c4 d e f”, “4/4”); now you must put the time signature string into the text itself, as corpus.parse(“tinynotation: 4/4 c4 d e f”). “cut” and “c” time signatures are no longer supported; use 2/2 and 4/4 instead. (2) calling tinyNotation.TinyNotationStream() directly doesn’t work any more. Use the corpus.parse interface either with the “tinynotation:” header or format=“tinynotation” instead. If you must use the guts, try tinyNotation.Converter(“4/4 c4 d e f”).parse().stream. (3) TinyNotation used to return its own “TinyNotationStream” class, which was basically incompatible with everything. Now it returns a standard stream.Part() (4) TinyNotation did not put notes into measures, etc. you needed to call .makeMeasures() afterwards. If you need the older method, use corpus.parse(‘tinynotation: 4/4 c2 d’, makeNotation=False)
• Musescore works as a PNG/PDF format. First run: us = environment.UserSettings(); us[‘musescoreDirectPNGPath’] = '/Applications/MuseScore 2.app/Contents/MacOS/mscore’ or wherever you have it). Then try calling “.show(‘musicxml.png’)” and watch the image arrive about 100x faster than it would in Lilypond. Thanks MuseScore folks! This is now the default format for .show() in iPython notebook. Examples using lily.png and lily.pdf will migrate to this format, so that lilypond can be moved to deprecated-but-not-to-be-removed status. (I just don’t have time to keep up)
• demos/gatherAccidentals : a good first test programming assignment for students. I use it a lot in teaching.
• musicxml parses clefs mid-measure (thanks fzalkow)
• installer.command updated for OS X (thanks Andrew Hankinson) — let me know if this makes a problem.
• postTonalTools demo in usersGuide.
• DataSet feature extractor gets a .failFast = False option for debugging.

Under the hood / contributors

• music21 now uses coverage checking via coveralls.io. We are at 91.5% code coverage; meaning when the test suite is run, 91% of all the lines of code are tested. Aiming for 95% (100% is impossible). Adding coverage checking let me find a lot of places that weren’t being tested that, lo and behold!, had bugs. What it means for contributors: any commit that is longer than 20 lines of code needs to improve the coverage percentage and help us get to 95%. So make sure that at least 92% (better 99%) of your code is covered by tests.
• the romanText.objects module has been renamed romanText.rtObjects to not conflict with external libraries. It’s an implementation detail.
• added qm_converter.py demo of how to subclass SubConverter.

Minor Changes

• measure number suffixes in musicxml output, not just input.
• language detector can detect Latin and Dutch language texts now.
• fix pitch class errors in microtones.
• midi files with negative durations no long crash the system.
• bugs fixed in tonalCertainty. You can be more certain that it works.
• cPickle is used in Python3 now. Faster.
• midi parsing can specify quantization levels.
• music21.__version__ gives the version (maxalbert did a lot this commit; forgot to shout out before!)
• better detection of lilypond binaries.
• certain Sibelius MusicXML files with UTF-16BOMs can now be read.
• rests imported from MusicXML would not have expressions attached to them — fermatas, etc. fixed
• serial.ToneRow() now has the notes each as quarter notes rather than as zero-length notes; it makes .show() possible; backwards incompatible for the small number of people using it.
• colored notation now works better and in more places.
• better docs.
• about a trillion tiny bugs and untested pieces of code identified and fixed by glasperfan (Hugh Z.)

Looking forward to the 2.1 release!

[April 11, 2015 13:47 pm] « » [music21]
The RILM blog, Bibliolore, published a recent post about the early history of computational musicology:

In the 1940s Bertrand Harris Bronson became one of the first scholars to use computers for musicological work.
For one of his projects he encoded melodic characteristics of hundreds of tunes collected for the traditional ballad Barbara Allen on punch cards, so a computer could ferret out similarities. His project resulted in four groups of tunes, members of which came from both sides of the Atlantic with varying frequency.
Read more at their site.  The RILM blog is amazing in any case.
[March 14, 2015 14:28 pm] « » [music21]
The master of empirical music studies and the inventor of Humdrum, David Huron, announced a workshop to be held in late May in Columbus, Ohio -- probably of great interest to anyone working with music21 who wants to put their work into a broader context:

Methods in Empirical Music Research: A Workshop for Music Scholars.
Monday May 18 to Friday May 22, 2015.
School of Music, Ohio State University

We are pleased to announce a workshop on empirical methods in music research. This is an intensive five-day workshop taught by Prof. David Huron.

The workshop will be of interest to anyone wishing to expand or enhance their research skills in music. Participants will learn how to design and carry out music experiments, and how to apply empirical, systematic and statistical techniques to problems in music history, analysis, performance, education, culture, policy, and other areas. The workshop is designed specifically to develop practical research skills for musicians and music scholars with little or no previous background in empirical methods.

The workshop introduces participants to a number of methods, including descriptive, exploratory and questionnaire methods, field research, interview techniques, correlational and experimental methods, hypothesis testing, theory formation, and other useful research tools and concepts. Participants will also learn how to read and critique published empirical research related to music - identifying strengths and weaknesses in individual music-related studies.

The workshop objectives will be pursued through a series of day-long activities, including lectures and demonstrations, interspersed with twenty hands-on and group activities.

Three different forms of registration are available for workshop participants. The fee for non-credit participation is $450. A fee schedule for continuing education, and graduate course credit (2 credit hours) is pending. Participants are responsible for their own transporation, food and accommodation. For further details, see http://musiccog.ohio-state.edu/home/index.php/Workshop [January 15, 2015 12:37 pm] « » [music21] An important milestone for music21 passed unnoticed by me a few weeks ago: ten years since the first time that code (well mostly documentation and tests) that still remains somewhere in the music21 codebase was run and did something useful (a scrambled loop for a composition project I was working on called Fine dead sound, after Faulkner). It seemed worth saying a bit about the history of the project and things learned along the way. Music21 started as a Perl project -- the oldest code I can find that even vaguely resembles the current music21 comes from November 2003, a 30k Perl script to label a Bach chorale with Roman numerals and correct keys (I still need to publish the algorithm somewhere since I haven't seen a better one). It had no graphical output except using David Rakowski's Lassus font. I was able to get it back up and running and through the modern miracle of web fonts, everyone (except IE users) can play with the oldest music21 system at: http://www.trecento.com/test/lassus.cgi?num=260. If I remember correctly, chords in red had only a passing functionality, the small letters are the roots of chords and the second line of text is the locally active key. Pivot chords are labeled in brackets. This was done for an assignment in Avi Pfeffer's AI and Music class; others in my group had already produced the code (in C I believe) for removing passing tones from the score. I had begun that project using Humdrum, a system I knew well and still have great admiration for, but I began to need to encapsulate more and more items into individual classes. I googled around, because I figured someone would have already gotten far in an object-oriented replacement for Humdrum. But I found nothing, so when I got back to the project about a year later I started creating generalized objects which I incorporated into a package called "PMusic" for "Perl Music." (I think I first called it just "Music" but realized that this was going to be a problem.) Here is part of the PMusic code for Chords, written on 12/31/2004. Good documentation was already a music21 principle, but names of notes were still based on Kern/Humdrum: =head1 PMusic::Chord (class) class for dealing with chords$ch1 = PMusic::Chord->new(['CC', 'E', 'g', 'b-']);

Note double set of brackets, indicating a perl array reference.
Doesnt deal with rests yet.  Chords of more or less than four notes might
be odd...

Can also give an arrayRef of Note objects if you're that perverse...

=cut

package PMusic::Chord;
use strict;
use Carp;

sub new {
my $proto = shift; my$class = ref($proto) ||$proto;
my %args;

## if only one arg, assume it's an arrayref of Note names
if (scalar @_ == 1) { $args{Notes} =$_[0] }
else { %args = @_ };
my $self = \%args; bless$self, $class; } ### for now, first note is always bass of chord (does tenor ever go below bass? sometimes!) =item NoteObjs() Returns an array ref of PMusic::Note objects =cut sub NoteObjs { my$self = shift;
return $self->{NoteObjs} if$self->{NoteObjs};
my @objs = ();
foreach (@{$self->{Notes}}) { if (ref($_)) { push @objs, $_; } else { push @objs, Note->new($_); }
}
$self->{NoteObjs} = \@objs; } =item Bass([note PMusic::Note]) returns the bass note or sets it to note. Usually defined as the first noteObj but we want to be able to override this. You might want an implied bass for instance... v o9. =cut sub Bass { my$self = shift;
$self->{Bass} =$_[0] if defined $_[0];$self->{Bass} ||= $self->NoteObjs->[0]; return$self->{Bass};

}

At this point I was living in Rome at the American Academy as a Rome Prize fellow in Medieval Studies, and halfway through my fellowship I realized that none of this code was going to write a six-hundred page dissertation on fourteenth-century music fragments, and besides, I had job interviews to prepare for, and later, students to teach at Smith College, Mount Holyoke College, and then MIT, none of which (yes, including MIT) cared that I was working on generalized software for musical analysis as a side project. I also saw how long this project was going to take.  And besides, I was still convinced that someone had already written a generalized OO toolkit for musical analysis, I just wasn't searching well enough.  So the project was put aside for almost two years before it reemerged in Python, as the (to be written) Part 2 explains.
[January 11, 2015 17:14 pm] « » [music21]
We're happy to announce that the first public alpha of music21 v.2 has been released!

Version 2 is the first version of music21 since v.1 to make substantial changes in the code base that introduce backwards incompatibilities in order to make going forward faster and smoother.  It doesn't change anything super fundamental à la Python 3's print function, so most code should still run fine, but definitely test in a separate environment before upgrading on any code you have that needs to run without problems.  The system is still changing and more backward-incompatible changes could be included until v.2.1.

We have had 420 commits since the last release, so there is a lot that is new!

Substantial changes include:

• Offsets and quarterLengths are now stored internally as Fractions if they cannot be exactly represented as floating point numbers. A lot of work went into making this conversion extremely fast; you probably won't ever notice the speed difference, but you can now be sure that seven septuplets will add up to exactly a half note.  For instance:
• >>> n = note.Note()
>>> n.duration.appendTuplet(duration.Tuplet(3,2))
>>> n.fullName
'C in octave 4 Quarter Triplet (2/3 QL) Note'
>>> n.quarterLength
Fraction(2, 3)
>>> n.quarterLengthFloat # if you need it...
0.6666666666666666
• Converter structure has been overhauled for more easily adding new converters in the future. If you've wanted to write a converter or already have one for a format not supported but have been daunted by how to include it in music21 now is a great time to do it.  Speaking of which...
• MEI format is supported for import (thanks to Chris Antila and the ELVIS team at McGill university for this great enhancement)
• Python 2.6 is no longer supported. All tests and demos pass and run on Python 2.7, 3.3, and 3.4. (3.2 and older are not supported)
• FreezeThaw on Streams works much better and caching loaded scores works great (some of this was included in 1.9, so definitely upgrade at least to that.
• Much improved Vexflow output using music21j, Javascript/Vexflow rendering engine. Was in 1.9, but improved here.
• Lots of places that used to return anonymous tuples, now return namedtuples for more easily understanding what the return values mean.
• Integrated Travis-CI testing and Coverage tests will keep many more bugs out of music21 in the future.
• Many small problems with Sorting and stream handling fixed.
• Corpus changed: for various licensing reasons, v.2.0 does not include the scores from the MuseData corpus anymore. This change mostly affects Haydn string quartets and Handel's Messiah.  However, new replacement scores are being included and 2.1 will have as many great works as before.  The MuseData scores are still available online.  MuseData is now a deprecated format and no further testing on it will be conducted; only bug fixes that are easily implemented will be accepted.
• music21 is now available under the BSD license in addition to LGPL!

We will try to stick to something close to the semantic versioning model in the future once v.2.1 is released. In other words, after 2.1, we'll try very hard not to break anything that worked in v.2.1 until v. 3.0 is released.  This will probably mean that the version numbers are going to creep up faster in the future.

Still todo before v.2.1 is a major change in how elements are stored in Streams.  Stay tuned if you care about performance tweaks etc., otherwise ignore it -- we'll keep the interface the same so you might not notice anything except speed improvements.

Smaller backward-incompatible changes include:
• Stream __repr__ now includes a pointer rather than a number if .id is not set.  This change will make filtering out doctests easier in the future.
• TinyNotation no longer allows for a two-element tuple where the second element is the time signature.  Replace: ("C4 D E", "3/4") with ("tinynotation: 3/4 C4 D E")
• Obscure calls in SpannerBundle have been removed: spannerBundle.getByClassComplete etc.
• Convenience classes: WholeNote, HalfNote, etc. have been removed.  Replace with Note(type='whole') etc.
• Old convenience classes for moving from Perl to Python (DefaultHash, defList) have been removed or renamed (defaultlist)
• Articulations are marked as equal if they are of the same class, regardless of other attributes.
• common.almostLessThan, etc. are gone; were only needed for float rounding, and that problem is fixed.
• duration.aggregateTupletRatio is now aggregateTupletMultiplier, which is more correct.
• common.nearestMultiplier now returns the signed difference.
• layout -- names changed for consistency (some layout objects had "startMeasure" and some "measureStart" - now they're all the same); now all use namedtuples.
• rarely used functions in Sites, base, Duration, SpannerStorage, VariantStorage, have been removed or renamed.  I'd be surprised if these affect anyone outside the development team.
Improvements and bug fixes:
• common.mixedNumeral for working with large rational numbers
• common.opFrac() optionally converts a float, int, or Fraction to a float, int, or Fraction depending on what is necessary to get exact representations. This is a highly optimized function responsible for music21 working with Fractions at about 10x the speed of normal Fraction work.
• Rest objects get a .lineShift attribute for layout.
• staffDetails, printObject MXL had a bug, writing out "True" instead of "yes"
• staffLines is now an int not float. (duh!)
• better checks for reused pointers.
• lots of private methods are now ready for public hacking!
• Lyric.rawText() will return "hel-" instead of "hel" for "hel-lo".

## How can I contribute?

Music21 is a rapidly-progressing project, but it is always looking for researchers interested in contributing code, questions, freely-distributable pieces, bug fixes, or documentation. Please contact Michael Scott Cuthbert (cuthbert at mit.edu), Principal Investigator.

The development of music21 has been supported by the School of Humanities, Arts, and Social Sciences at M.I.T., the Music and Theater Arts section, and generous grants from the Seaver Institute and the NEH/Digging-Into-Data Challenge. Further donations to the project are always welcome.